The Red Devils swooped in January to shock Manchester City and sign the Chilean from Arsenal.

City had long been favourites to take Sanchez, who was keen to move, and reunite him with Pep Guardiola.

But his hefty demands and the substantial costs saw City pull out as United leaped at the chance to snap the 29-year-old up.

Purslow, having dealt with a number of top level transfers during his time at Liverpool, feels there was a breach of trust by Sanchez towards the Premier League leaders.

And that ultimately led to United winning the auction, pleasing both Mourinho and Arsenal, who took Henrikh Mkhitaryan and £20m in exchange.

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Alexis Sanchez joined Man Utd from Arsenal after Man City withdrew their interest last month

Every Premier League club's transfer window graded

HOW did each Premier League club get on in the January transfer window?

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Arsenal - A: Despite losing star man Alexis Sanchez, the Gunners got Henrikh Mkhitaryan in exchange and then brought in Pierre-Emerick Aubameyang. They also kept hold of Mesut Ozil and tied him down to a new contract

"We will never quite know the sequence of events that led to that potential transaction winding away into a United purchase.

"It has the look from the outside, I don't know this to be true, that Arsenal out of nowhere had their dreams come true.

"Rather than being in a unilateral discussion with City taking their best player nearly on a free they had a little auction going when Mourinho and Antonio Conte both spoke up in early January that actually getting Sanchez was a once in a generation opportunity to buy a top player for not much money down.

"I think Arsenal suddenly had a little auction going. I suspect when Sanchez's agent said to Manchester City's executive team you might have to improve my deal up a bit because United are here - that [would have] felt like a breach in trust.

"They thought they had a handshake deal at best. I bet they were very angry about that and I suspect they thought actually let's walk away from this deal leaving Manchester United to sweep him up.

"Brilliant outcome for United, pretty good outcome for Arsenal on balance but I suspect not a very happy camp at City around the way that deal was conducted."

Sanchez is set to make his Old Trafford debut on Saturday when Manchester United host Huddersfield (3pm).